In modern internal combustion engines, variable valve drives, with which different valve strokes can be set at the gas exchange valves of the internal combustion engine, are used to optimize the charge movement in the combustion chamber. DE 196 11 641 C1, which is incorporated by reference, discloses a valve drive of an internal combustion engine which permits a gas exchange valve to be activated with a plurality of different stroke curves. For this purpose, a sliding cam having a plurality of cam tracks is mounted in a rotationally fixed but axially displaceable fashion on the camshaft, which sliding cam has a stroke contour into which an activation element in the form of a pin for generating axial displacement of the cam engages. The axial displacement of the cam causes a different valve stroke to be set at the respective gas exchange valve.
DE 10 2008 060 166 A1, which is incorporated by reference, discloses a valve drive in which a sliding cam which is mounted in a rotationally fixed but axially displaceable fashion on a camshaft has a sliding block section with a plurality of grooves, and in which in order to bring about axial displacement of the sliding cam an actuator having a plurality of pins which can be activated is provided. The sliding block section has a first, right-handed groove and a second, left-handed groove which are arranged one next to the other on the circumference of the sliding block section and merge with a common run-out groove. The pins of the actuator interact with the grooves of the sliding block section.
In addition, a valve drive is already known in which the grooves of the sliding block section are positioned one behind the other on the circumference of the sliding block section, specifically a first groove for axial displacement of the sliding cam in a first direction and a second groove for axial displacement of the sliding cam in an opposing second direction. In this valve drive, the actuator also has a plurality of pins which can be activated in order to bring about axial displacement of the sliding cam, specifically a first pin for axial displacement of the sliding cam in the two directions about a first axial segment and a second pin for axial displacement of the sliding cam in the two directions about a second axial segment.
For the engine control of an internal combustion engine having such a valve drive which has at least one displaceable sliding cam, it is necessary to have knowledge of the relative position of the sliding cam on the camshaft and therefore of the cam tracks relative to the gas exchange valve of the internal combustion engine which is to be activated. Hitherto, it was difficult to detect in a certain and reliable way the relative position of the sliding cam on the camshaft and therefore the relative position of the cam tracks with respect to the gas exchange valve which is to be activated.